The present invention relates to a traumatologic device, and, more particularly, to an improved traumatologic device for reducing long-bone fractures that require external fixation.
A variety of traumatologic devices for reduction of bone segments are known in the art. For example external bone fixation devices (commonly referred to as external fixators) are known. Typically external fixators are used to reduce fractures of the long bones in the human body. These devices are always placed in position under anesthesia. In order to reduce the duration of the anesthesia, fixator devices have been developed to allow positioning at every possible angle, while still allowing easy adjustment by a surgeon.
The early development of external fixator devices, such as that exemplified by U.S. Pat. No. 2,250,417 to Ettinger, was aimed at producing a simple and lightweight fracture reduction device which is practical to leave in place to serve as a retention device, thereby rendering a cast unnecessary. As disclosed, the Ettinger device allows two separate sets of dual bone pins or screws, each transcutaneously installed in the bone on either side of a fracture, to be connected and fixed at variable points to a single bone fixation rod running roughly parallel to the longitudinal axis of the affected bone. This resultant connection of opposing pin/screw sets provides the immobilization necessary to allow proper healing of the fracture. Ettinger discloses the use of multiple sleeve and post connections between the bone pins/screws and the bone fixation rod to allow the bone pins or screws to be installed at varying angles relative to the bone fixation rod. Ettinger additionally discloses the use of a rod and sleeve configuration whereby one of the two bone pin/screw couplings is fixed to the bone fixation rod, while the second comprises an internally threaded sleeve that is threaded over the opposite end of the bone fixation rod, and whose position is adjustable relative to the fixed coupling via rotation of the bone fixation rod.
Later improvements on the Ettinger design, such as that disclosed by U.S. Pat. No. 4,135,505 to Day, allow for the installation of an increased and/or variable number of bone pins on each side of the fracture. This provides the advantage of giving the practitioner more options in the spacing of pins, and of avoiding installing a pin at a particular point on the bone if such placement was undesirable. The Day device additionally discloses a bone pin clamp incorporating a ball and socket connection to allow for varying bone pin installation angles.
Further improvements such as those disclosed by U.S. Pat. No. 5,160,335 to Wagenknecht, U.S. Pat. No. 5,219,349 to Krag, U.S. Pat. No. 5,624,440 to Huebner, U.S. Pat. No. 5,891,144 to Mata et al., and U.S. Pat. No. 6,022,348 to Spitzer disclose bone pin/screw clamps which incorporate more modern universal joint assemblies to allow easier adjustment of the distance between bone pin clamps along the length of the bone fixation rod when the attached bone pins/screws are installed at multiple angles relative to the immobilization rod. Moreover the Krag, Huebner, Mata et al., and Spitzer devices provide easier means to adjust the relative distance between bone pin couplings on opposing sides of a fracture (accomplished by simple sliding in the Krag, Huebner, Mata et al., and Spitzer devices, and by incremental rotation of an attached screw and nut combination in the Day and Wagenknecht devices). Yet a further improvement is disclosed in the Wagenknecht patent, which provides springs between the bone pin clamp faces to spread the faces and thereby facilitate introduction of the bone pins.
The difficulty with the Huebner, Krag, Wagenknecht and Day devices is that their means of fixing the bone pin clamp to the bone fixation rod is by way of a closed hole and screw combination. To facilitate installation of these fixators, the bone pin clamps must be threaded onto the bone fixation rod from one end of the rod, making installation cumbersome. The Mata et al., and Spitzer devices address this problem by providing bone pin clamps that attach to the bone fixation rod utilizing open-face jaws. This design allows the device to be engaged with the rod by simply placing it onto the desired location along the length of the rod, without the need for threading as in the Mata et al. and Spitzer devices. The difficulty with the Mata et al. and Spitzer devices is that their open-faced bone pin clamp jaws are two-piece designs which by their nature cannot be self-sprung and so require the use of an additional piece, such as a coil or compression spring, to maintain the jaws in an open position during installation onto the bone fixation rod. Additionally, the two piece nature of their design increases unit fabrication difficulty and cost.
Accordingly, there is a need in the art to provide a simpler design bone pin clamp assembly that minimizes the total number of steps an operator must take to engage the clamp assemblies and bone fixation rod, while still providing maximum flexibility to the operator in adjusting the distance between bone pin clamps on either side of a fracture.
The present invention addresses the need in the art by providing a bone fixation rod attachment assembly which allows a surgeon to snap the assembly onto one or more bone fixation rods, to provide loose capture of the rod in a minimum number of steps, and with a minimum of attention, and while retaining the flexibility of providing for the locking of multiple bone pins installed at multiple angles, on opposite sides of a fracture.
In particular, the present invention provides an external fixator for reducing fragments of a bone, comprising a bone fixation rod, at least two sets of bone pins, and a bone pin locking assembly comprising a pin vise, a bone fixation rod attachment portion having a single-piece fixation rod clamp, and a coupling to provide relative rotation in two axes between the pin vise and the fixation rod attachment portion. The single piece fixation rod clamp comprises a jaw portion which permits engagement of the bone fixation rod when the single-piece fixation rod clamp is pressed onto the bone fixation rod from the side of the bone fixation rod. This action loosely couples the bone pin locking assembly to the bone fixation rod. This loose coupling may be achieved by providing the single-piece fixation rod clamp with a jaw portion, having first and second opposing jaws, the clearance between these jaws being slightly smaller than the outside diameter of the bone fixation rod. An interference is thereby established between the single-piece fixation rod clamp jaw and the bone fixation rod when the rod is initially installed into the jaw. The first and second opposing jaws further connect to adjoining spring arms, which themselves converge into a single cylindrical coupling end. When the first and second opposing jaws are positively displaced with respect to their rest position, a resulting spring force is generated which tends to force the jaws back to their rest position. In this way, the bone fixation rod may be snapped into the jaw portion by the surgeon applying the requisite pressure.
The present invention also provides for the immobilization of the bone pin locking assembly along the bone fixation rod so the locking assembly may neither move nor rotate. This may be achieved by the use of a bolt disposed between the opposing jaws of the single-piece fixation rod clamp jaw portion. Immobilization occurs through the tightening of the bolt, which draws the jaws together to a final, locked, position.
The present invention also enables the bone pin locking assembly to engage the bone fixation rod by pressing the single-piece fixation rod clamp into the bone fixation rod in a direction substantially along the rod clamp longitudinal axis, or in a direction substantially perpendicular to the bone fixation rod longitudinal axis.
The present invention further provides cooperating serrations on the bearing faces of the pin vise portion and the single-piece fixation rod clamp coupling. These serrations serve to prevent relative rotational movement between the single piece fixation rod clamp and the pin vise upon final tightening of a coupling bolt. The present invention additionally provides a spring, located between the serrated bearing faces of the pin vise portion and the single-piece fixation rod clamp coupling. This spring provides a force tending to separate the coupling and the pin vise portion to allow free relative rotational movement between the two pieces prior to final tightening of the coupling bolt, or subsequent to loosening of the coupling bolt.
The present invention further provides grooves in the pin vise clamping faces that captivate the bone pins when the engaging faces are clamped together. These clamping grooves may be of cylindrical, or generally arcuate, cross section, or they may be of triangular cross section. In any case the grooves in each clamping face are designed to contact the bone pins along less than 180 degrees of the circumference of each bone pin.
The present invention also provides a method for treating a fractured bone, comprising the insertion of at least two sets of bone pins into the bone on opposite sides of a fracture, and installing on those bone pins first and second bone pin locking assemblies each comprising a pin vise portion, and a rod attachment portion comprising a rotatable coupling and a single-piece fixation rod clamp. The pin vise portion of the first bone pin locking assembly engages at least one bone pin on the first side of the fracture, and the pin vise portion of the second bone pin locking assembly engages at least on bone pin on the second side of the fracture. The jaw portion of each single-piece fixation rod clamp is then snapped onto a bone fixation rod along a direction perpendicular to the longitudinal axis of the fixation rod. Each bone pin locking assembly is then adjusted to its final position and orientation, whereupon the assemblies are immobilized along the bone fixation rod. The present invention further provides for this immobilization by the tightening of a bolt disposed within the bone pin locking assembly jaw portion.
In particular, the treatment method of the present invention may be utilized for consolidation of bone portions, where the opposing portions of fractured bones are forced together prior to immobilization. The present invention may also be utilized to facilitate distraction of opposing segments of bone, so as to permit osteosynthesis in the region between the opposing bone segments.